Thermoneutral N-H Bond Activation of Ammonia by a Geometrically Constrained Phosphine

A geometrically constrained phosphine bearing a tridentate NNS pincer ligand is reported. The effect of the geometric constraint on the electronic structure was probed by theoretical calculations and derivatization reactions. Reactions with N-H bonds result in formation of cooperative addition products. The thermochemistry of these transformations is strongly dependent on the substrate, with ammonia activation being thermoneutral. This represents the first example of a molecular compound that reversibly activates ammonia via N-H bond scission in solution upon mild heating.

Automated summary

A geometrically constrained phosphine bearing a tridentate NNS pincer ligand has been successfully used to reversibly activate ammonia through N-H bond scission upon mild heating in solution, as demonstrated through experimental and theoretical studies. The geometric constraint also leads to the formation of cooperative addition products, and the thermodynamics of these transformations are substrate-dependent.